Introduction: Prevention of bone loss has been an active area of osteoporosis research for many years. Regular exercise, calcium intake, and vitamin D intake are well known to help prevent bone loss in women both with and without osteoporosis. Studies have shown that women over 65 years of age need optimally around 1500mg of calcium per day to help prevent bone loss. Recently, 1200mg of calcium has been shown to be beneficial in preventing bone loss in men. This study proposes that increasing dietary calcium to 1500mg per day in elderly men will reduce age-related bone loss. Methods: Eighty-four men 65 years and older were screened for the study. Inclusion required men to have bone mineral density (BMD)of the femoral neck between 0.5 SD above and 1.0 SD below age-matched controls, calcium intake of less than or equal to 1000mg per day, and to have no active bone disease. Subjects were randomized in a double-blind, controlled trial to either placebo or to calcium to supplement their total calcium intake to 1500mg per day. Patients were followed every three months with repeat BMD at one year. Results: Forty men were randomized to the study; 7 withdrew - 5 due to scheduling conflict, 1 reported impotence, and 1 acute myocardial infarction. Average age was 76 years: 74 Caucasian and 2 non- Caucasian. Of 33 men, 15 were randomized to placebo, and 18 to dietary supplementation with calcium carbonate. Compliance was greater than 80% throughout the study with an average compliance by pill count of 96%. At one year, BMD at the femoral neck decreased by 0.01mg/cm in the placebo group compared with 0.006mg/cm in the calcium supplemented group. Bone density at L1-L4 spine, trochanter, and total hip had similar decreases in BMD, without detectable differences between the groups.(Note: the man reporting impotence was in the placebo group). Discussion: Calcium carbonate supplementation was well tolerated by this group of elderly men. The findings at one year indicate a difference in the rate of bone loss may be less than in the calcium-supplemented group (t- test> 0.65). This result may be explained by bone transients or may be actual changes in BMD. Other covariates of activity level, hormonal levels, or genetics may be important in this analysis. The sample size may be too small to detect changes in BMD after one year of intervention. Follow-up at two years may either confirm or refute these findings.